Solar array with reference solar power plant for improved management

ABSTRACT

Solar array ( 1 ) comprising solar modules ( 3 ) distributed in rows ( 10 ), each solar module comprising solar collector ( 5 ) carried by a single-axis solar tracker ( 4 ), a reference solar power plant ( 2 ) comprising a central reference solar module and at least one secondary reference solar module, and a piloting unit ( 7 ) adapted for:
         piloting the angular orientation of the central reference module according to a central reference orientation setpoint corresponding to an initial orientation setpoint,   piloting the orientation of each secondary reference module according to a secondary reference orientation setpoint corresponding to the initial orientation setpoint shifted by a predefined offset angle;   receiving an energy production value from each reference module;   piloting the orientation of the modules, except for the reference modules, by applying the reference orientation setpoint associated to the reference module having the highest production value.

The present invention relates to a solar array comprising a plurality ofsolar modules distributed in several parallel rows, as well as to amethod for managing such a solar array.

It relates more particularly to a solar array in which each solar modulecomprises at least one solar collector, in particular of thephotovoltaic panel type, carried by a single-axis solar tracker, whereineach solar tracker is piloted in rotation about a main axis by means ofan actuator for a rotation of the solar module allowing tracking the Sunduring its rise and set from east to west.

The invention therefore concerns the field of solar arrays comprisingsolar trackers, otherwise called solar tracker support systems,distributed in parallel rows and supporting solar collectors, whereinthe solar trackers are of the single-axis type that is to say rotatingalong a single main axis, for a rotation allowing tracking the Sunduring its rise and set from east to west. For accuracy, such a mainaxis extends generally horizontally and substantially parallel to theground on which the solar tracker is anchored.

Within the same row, the solar trackers are aligned, with their mainaxes substantially coincident, generally in a north-south direction.

In a conventional solar array, it is known to provide a piloting unit ofthe angular orientation of the solar modules, wherein the piloting unitis connected to the actuators to servo-control the angular orientationof the solar modules by applying a common orientation setpoint to allsolar modules.

This common orientation setpoint is generally established on the basisof an astronomical calculation of the position of the Sun, for areal-time positioning facing the Sun, with possibly horizontalflattening phases of the solar collectors, at the beginning and the endof the day. This common orientation setpoint depends in particular onthe date, because the position of the Sun varies from one day to anotherthroughout the seasons.

However, this type of servo-control based only on the astronomicalcalculation of the position of the Sun, has a major drawback by offeringa yield deficit under certain meteorological conditions, and inparticular in cloudy conditions which are causes of diffuse solarradiation. The diffuse solar radiation occurs when the direct solarradiation is dispersed in the clouds and the atmospheric particles. Thediffuse solar radiation results from the diffraction of light by theclouds and the various molecules in suspension in the atmosphere. Thediffuse solar radiation therefore does not necessarily follow thedirection defined by the Sun in the direction of the observation pointon the Earth's surface. Consequently, under cloudy conditions, it may bepreferable, in order to obtain a maximum yield with regards to theseconditions, to orientate the solar trackers or modules on an orientationcalled indirect or diffuse orientation which does not necessarilycorrespond to the direction of the direct solar radiation.

Furthermore, the solar collector may be of the double-sided type, thatis to say with an upper productive face facing the Sun and a lower facealso productive facing the ground. The lower face receives the solarradiation reflected by the ground, generally called albedo. Thus,depending on the albedo, it may be preferred, in order to obtain amaximum yield, to orientate the solar trackers or modules on anorientation called indirect orientation which does not necessarilycorrespond to the direction of the direct solar radiation.

The present invention aims to solve these drawbacks by proposing a solararray, and an associated management method, which allowservo-controlling the solar modules on a common orientation setpointwhich will take into account, at least partially, the diffuse radiationand/or the albedo.

To this end, it proposes a solar array comprising a plurality of solarmodules distributed in several parallel rows, each solar modulecomprising at least one solar collector, in particular of thephotovoltaic panel type, carried by a single-axis solar tracker, whereineach solar tracker is piloted in rotation about a main axis by means ofan actuator for a rotation of the solar module allowing tracking the Sunduring its rise and set from east to west, said solar array furthercomprising a piloting unit of the angular orientation of the solarmodules, said piloting unit being linked to the actuators toservo-control the angular orientation of the solar modules by applying acommon orientation setpoint to all solar modules, said solar array beingnoteworthy in that it comprises a reference solar power plant comprisingat least two reference solar modules, including a central referencesolar module and at least one secondary reference solar module, whereinthe piloting unit is adapted for:

-   -   piloting the angular orientation of the central reference solar        module according to a reference orientation setpoint called        central reference orientation setpoint corresponding to an        initial orientation setpoint,    -   piloting the orientation of the or each secondary reference        solar module according to a reference orientation setpoint        called secondary reference orientation setpoint, said secondary        reference orientation setpoint corresponding to the initial        orientation setpoint shifted by a predefined non-zero angle        called offset angle associated to said secondary reference solar        module, the central reference solar module being accordingly        associated to a zero offset angle;    -   receiving a solar energy production value from each reference        solar module;    -   piloting the angular orientation of the solar modules, except        for the reference solar modules, by applying as a common        orientation setpoint the reference orientation setpoint        associated to the reference solar module having the highest        solar energy production value.

Thus, the reference solar power plant will allow testing an initialorientation setpoint (for example a direct solar radiation trackingsetpoint) and at least one secondary reference orientation setpoint(advantageously several secondary reference orientation setpoints)angularly shifted relative to the initial orientation setpoint of anoffset angle. Most of the time, it is the initial orientation setpointwhich will be applied, but in the case of cloud, and therefore ofdiffuse radiation, and/or in case of a high albedo, a shift of an offsetangle may prove to offer a better solar energy production, and thereforethe reference solar power plant will allow noticing that a secondaryreference orientation setpoint associated to an offset angle is to beprivileged, and therefore the piloting unit will implement a shift ofthe offset angle for the set of solar modules, except for the referencesolar modules. The more secondary reference solar modules are, the moreit will be possible to test different offset angles.

This solution is in particular simple and inexpensive to implement,while providing an improvement in the overall solar energy production ofthe solar array, since it directly takes into account the solar energyproduction for one or more offset angle(s) about the initial orientationsetpoint.

According to a feature, the reference solar power plant comprisesseveral secondary reference solar modules each associated to a dedicatedoffset angle.

According to another feature, the reference solar power plant comprisesa number N of secondary reference solar modules associated to positiveoffset angles and a number M of secondary reference solar modulesassociated to negative offset angles, wherein N and M are integers.

Four general configurations are possible:

-   -   if N=M≠0, then the reference solar power plant comprises at        least one pair of secondary reference solar modules associated        respectively to a positive offset angle and to a negative offset        angle.    -   if N≠0 and M=0, then the reference solar power plant comprises        only secondary reference solar modules associated to positive        offset angles;    -   if N=0 and M≠0, then the reference solar power plant comprises        only secondary reference solar modules associated to negative        offset angles;    -   if N≠0, M≠0 and N≠M, then the reference solar power plant        comprises a different number of secondary reference solar        modules associated to positive offset angles than that of        secondary reference solar modules associated to negative offset        angles.

In a particular embodiment, at least one deviation between two adjacentoffset angles is less than 3 degrees in absolute value; one of these twooffset angles being may correspond to the zero offset angle of thecentral reference solar module.

In other words, the angular shift between the orientation setpoints ofat least two adjacent reference solar modules does not exceed 3 degrees,which is sufficient to test different offset angles.

It should be noted that the deviation between two adjacent offset anglesmay be constant or on the contrary not be constant.

According to a possibility of the invention, the solar array comprises,at an input of the piloting unit, a calculation unit of the initialorientation setpoint depending on an astronomical calculation of theposition of the Sun.

It is also possible to consider that the calculation unit is adapted tocalculate the initial orientation setpoint depending on at least one ofthe following parameters: minimum and maximum orientations accessible tothe solar trackers, shadings of the solar modules of a row on the solarmodules of an adjacent row.

According to another possibility of the invention, the piloting unit isadapted to pilot the angular orientation of the solar modules, exceptfor the reference solar modules, by applying as a common orientationsetpoint the secondary orientation setpoint applied to a secondaryreference solar module having the highest solar energy production value,only if this secondary reference solar module has the highest solarenergy production value for a predefined waiting time.

Thus, a waiting time is set before switching to a secondary orientationsetpoint, to avoid changing the orientation more or less often and moreor less quickly. Indeed, each orientation change solicits at least oneactuator (generally an electric motor), generating an electricalconsumption and a wear of the mechanical members solicited by theorientation change (bearings, elements for guiding in rotation, . . . ).These electrical consumptions and these wears will not necessarily becompensated by the productivity gains obtained by matching the secondaryorientation setpoints.

The invention also relates to a method for managing a solar array inaccordance with the invention, said method comprising the followingsteps carried out repeatedly:

-   -   calculating an initial orientation setpoint;    -   piloting the angular orientation of the central reference solar        module according to a reference orientation setpoint called        central reference orientation setpoint corresponding to the        initial orientation setpoint;    -   piloting the orientation of the or each secondary reference        solar module according to a reference orientation setpoint        called secondary reference orientation setpoint, said secondary        reference orientation setpoint corresponding to the initial        orientation setpoint shifted by a predefined non-zero angle        called offset angle associated to said secondary reference solar        module;    -   receiving a solar energy production value from each reference        solar module;    -   piloting the angular orientation of the solar modules, except        for the reference solar modules, by applying as a common        orientation setpoint the reference orientation setpoint        associated to the reference solar module having the highest        solar energy production value.

In accordance with an advantageous feature of the invention, if thehighest solar energy production value is associated to the secondaryreference orientation setpoint associated to a secondary reference solarmodule, then the method implements the piloting of the angularorientation of the solar modules, except for the reference solarmodules, by applying as a common orientation setpoint said secondaryreference orientation setpoint, only if this secondary reference solarmodule has the highest solar energy production value for a predefinedwaiting time.

Advantageously, the waiting time is established depending on at leastone of the following parameters:

-   -   an energy consumption necessary to modify the orientation of the        solar modules, except for the reference solar modules, the        offset angle associated to the secondary reference solar module        having the highest solar energy production value;    -   a wear rate of mechanical members of the solar trackers of the        solar modules, except for the reference solar modules, solicited        during a change of orientation of the offset angle associated to        the secondary reference solar module having the highest solar        energy production value.

The present invention also concerns the feature according to which thethe initial orientation setpoint is calculated depending on anastronomical calculation of the position of the Sun.

Other features and advantages of the present invention will appear uponreading the detailed description below, of a non-limiting implementationexample, with reference to the appended figures in which:

FIG. 1 is a schematic view of a solar array in accordance with theinvention;

FIG. 2 is a schematic perspective view of several rows of solar modulesin a solar array in accordance with the invention;

FIGS. 3 and 4 are schematic perspective views of two examples of areference solar power plant;

FIG. 5 is a representation in the form of a flowchart of the stepsimplemented during a management method in accordance with the invention;and

FIG. 6 is a schematic representation of a variation curve of the initialorientation setpoint as a function of time, at a given date.

FIG. 1 illustrates a solar array 1 in accordance with the invention,comprising several groups GR of several rows 10 of solar modules (thesesolar modules being not illustrated in FIG. 1 and seen in FIG. 2), thesegroups GR and these rows 10 being distributed and sized depending on themorphology of the ground which accommodates the solar array 1. The solararray 1 also includes a reference solar power plant 2 described later.

With reference to FIG. 2, each row 10 comprises several solar modules 3aligned in the north-south direction and arranged side by side withinthe row 10.

Each solar module 3 comprises a single-axis solar tracker 4 rotatingabout a main axis of rotation A, of the type comprising:

-   -   a fixed structure 40 for anchoring on the ground constituted,        for example, of one or more pylon(s) anchored to the ground for        example by beating, screwing, bolting, ballasting, or other        equivalent means allowing fastening and stabilizing the fixed        structure 40 on the ground;    -   a movable structure (not shown), in particular of the platform        type composed of an assembly of beams, stringers and/or cross        members, wherein the movable structure is mounted in rotation on        the fixed structure 40 along the main axis A, and in particular        mounted in rotation on the upper ends of the pylon(s);    -   a mechanical system for driving in rotation the movable        structure along the main axis A.

Each solar tracker 3 is piloted in rotation about the main axis Athereof by means of an actuator (not illustrated) for a rotation of thesolar module 3 allowing tracking the Sun during its rise and set fromeast to west. This actuator may be specific to each solar module 3, ormay be shared between several solar modules 3, for example within thesame row 10, or even two or more rows 10.

Each solar module 3 further comprises at least one solar collector 5,and in particular one or more photovoltaic panel(s), supported by ormounted on the movable structure of the solar tracker 4. For the rest ofthe description, the solar collectors are photovoltaic panels 5.

Referring to FIG. 2, the axis of rotation A is substantially horizontaland directed in the north-south direction. When the solar tracker 1 ishorizontal or flat down (as seen in FIG. 2), the photovoltaic panel(s) 5are horizontal and extending in a horizontal plane defined by alongitudinal axis X (parallel to the main axis A) in the north-southdirection and by a transverse axis Y in the east-west direction,orthogonally to a vertical axis Z.

For the rest of the description, the angular orientation, otherwisecalled inclination angle, of a solar module 3 (or angular orientation ofthe solar tracker 3 and of the photovoltaic panel(s) 5) corresponds tothe angle of the normal to the photovoltaic panel(s) 5 regarding to thevertical axis Z taken in a horizontal plane (X, Y). Accordingly, whenthe solar tracker 1 is horizontal or flat down (as schematized in FIG.2), this angular orientation is 0 degrees.

With reference to FIG. 5, the solar array 1 further comprises acalculation unit 6 adapted to calculate an initial orientation setpointCOI depending on an astronomical calculation of the position of the Sun.

FIG. 6 illustrates an example of variation of the initial orientationsetpoint COI as a function of time t, at a given date, over a time rangeof one day taken between 4 o'clock in the morning (4 AM) and 7 o'clockin the evening (7 PM). It should be noted that this variation has stagesof −50 degrees in the morning and +50 degrees in the afternoon,corresponding to the maximum and minimum orientations of the solarmodule 3, because the rotation of the solar module 3 is limited formechanical reasons.

This initial orientation setpoint COI may also be calculated dependingon other parameters, such as for example an optimization taking intoaccount the shading phenomena of the solar modules 3 of a row 10 on thesolar modules 3 of an adjacent row 10.

With reference to FIG. 5, the solar array 1 also comprises a pilotingunit 7 adapted to pilot the angular orientation of the solar modules 3of the rows 10 of the groups GR, this piloting unit 7 being linked tothe actuators of these solar modules 3 to servo-control their angularorientations by applying a common orientation setpoint COC to all thesesolar modules 3.

This piloting unit 7 is connected at an input to the calculation unit 6in order to receive as input data the initial orientation setpoint COIand is connected at an output to these solar modules 3 (and morespecifically to their actuators) in order to output the commonorientation setpoint COC which will be applied to all solar modules 3.

This piloting unit 7 is also connected to the reference solar powerplant 2 to establish this common orientation setpoint COC depending onthe initial orientation setpoint COI and also depending on a response ofthis reference solar power plant 2.

With reference to FIGS. 3 and 4, the reference solar power plant 2comprises a plurality of reference solar modules 20(i) (i relativeinteger), including a central reference solar module 20(0) and a severalsecondary reference solar modules 20(j) (j non-zero relative integer).In the example of FIGS. 3 to 5, the reference solar power plant 2comprises two pairs of secondary reference solar modules, namely a firstpair of secondary reference solar modules 20(+1), 20(−1), and a secondpair of secondary reference solar modules 20(+2), 20(−2).

The reference solar modules 20(i) are of the same type as the solarmodules 3 described above, but they may possibly have differentdimensions. The reference solar modules 20(i) thus comprise a trackersupport 4 movable in rotation along a main axis A and supporting atleast one solar collector 5 of the same technology as the solarcollectors 5 of the solar modules 3.

Within the reference solar power plant 2, these reference solar modules20(i) may for example be aligned orthogonally to their main axes A ofrotation (as shown in FIG. 3), or be aligned along their main axes A ofrotation.

The piloting unit 7 is adapted for:

-   -   piloting the angular orientation of the central reference solar        module 20(0) according to a reference orientation setpoint        called central reference orientation setpoint COR(0)        corresponding to the initial orientation setpoint COI (in other        words COR(0)=COI and an associated zero offset angle OFF(0));    -   piloting the orientation of each secondary reference solar        module 20(j) according to an associated secondary reference        orientation setpoint COR (j), this secondary reference        orientation setpoint COR(j) corresponding to the initial        orientation setpoint COI shifted by a predefined angle called        offset angle OFF(j) associated to the secondary reference solar        module 20(j) (in other words COR(j)=COI+OFF(j)).

Thus, the piloting unit 7 controls the angular orientation of thecentral reference solar module 20(0) so that it follows the curve of theinitial orientation setpoint COI. In addition, the piloting unit 7pilots the angular orientation of each secondary reference solar module20(j) so that it follows the curve of the initial orientation setpointCOI shifted from the offset angle OFF(j) dedicated to the secondaryreference solar module 20 (j).

For each pair of secondary reference solar modules 20(+1), 20(−1)(respectively 20(+2), 20(−2)), a secondary reference module 20(+1)(respectively 20(+2)) is associated to a positive offset angle OFF(+1)(respectively OFF(+2)) and the other secondary reference module 20(−1)(respectively 20(−2)) is associated to a negative offset angle OFF(−1)(respectively OFF (−2)). In addition, OFF(−1) and OFF(+1) (respectivelyOFF(−2) and OFF(+2)) are equal in absolute value.

In general, j=+k or −k (wherein k positive integer), and OFF(+k)=+Ak andOFF(−k)=−Ak, wherein Ak is a positive angle. In other words, thepositive offset angle (+Ak) and the negative offset angle (−Ak) of eachpair of secondary reference solar modules 20(+k), 20(−k) are equal inabsolute value.

It should be noted that the higher j is in absolute value (in otherwords, the higher k is), and the higher the offset angle OFF(i) (inother words OFF(+k) or OFF(−k)) is in absolute value.

In addition, the offset angles of smaller absolute value, that is to saythe offset angles OFF(+1) and OFF(−1), are less than or equal to 3degrees in absolute value. In other words, |OFF(+1)|=|OFF(−1)|=A1≤3degrees.

In addition, the deviation between two adjacent offset angles is lessthan or equal to 3 degrees in absolute value. In other words,|OFF(i)−OFF(i+1)|≤3 degrees and |OFF(i)−OFF(i−1)|≤3 degrees.

It may be considered that |OFF(i)−OFF(i+1)|=|OFF(i)−OFF(i−1)|=PA. Inother words, the pitch PA is constant between the offset angles, so thatOFF(i)=i·PA, with a zero offset angle OFF(0) for the central referencesolar module 20(0) (wherein i=0). This pitch PA is positive, non-zeroand less than or equal to 3 degrees. Therefore, OFF(+1)=PA, OFF(−1)=−PA,OFF(+2)=2·PA and finally OFF(−2)=−2·PA. Thus, we have the followinggeneral relation: COR(i)=COI+i·PA.

It is of course conceivable that the deviation between two adjacentoffset angles OFF(i) varies, in other words the pitch capable of beingnot constant.

It may be also considered to have more secondary reference solar modules21(j) associated to positive offset angles OFF(j), or conversely to havemore secondary reference solar modules 21(j) associated to negativeoffset angles OFF(j). In other words, it is conceivable that thereference solar power plant 2 comprises:

-   -   secondary reference solar modules 20(j) associated only to        positive offset angles OFF(j); or    -   secondary reference solar modules 20(j) associated only to        negative offset angles OFF(j); or    -   P1 secondary reference solar modules 20(j) associated to        positive offset angles OFF(j) and P2 secondary reference solar        modules 20(j) associated to negative offset angles OFF(j),        wherein P1 and P2 are non-zero integers and P1 different from P2        (P1 may be greater than or less than P2).

The number of secondary reference solar modules 21(j) and the choice oftheir offset angles OFF(j) (pitch, signs, values) depends in particularon the host site of the solar array 1 (configuration, environment suchas the presence of hills, mountains, water bodies, etc.) and of thetechnology of the solar collector 5.

Then, the piloting unit 7 implements the following steps:

-   -   receiving a solar energy production value P(i) from each        reference solar module 20(i);        -   addressing to the solar modules 3 (except for the reference            solar modules 20(i)), as common orientation setpoint COC,            the reference orientation reference COR(i) associated to the            reference solar module 20(i) having the highest solar energy            production value P(i).

Thus, the piloting unit 7 pilots the angular orientation of the solarmodules 3 by applying as common orientation setpoint the referenceorientation reference COR (i) associated to the reference solar module20(i) having the highest solar energy production value P(i). In otherwords, COC=COR(m)=COI+m·PA wherein P(m) corresponds to the maximum ofthe P(i).

If the highest solar energy production value is associated to thesecondary reference orientation setpoint COR(j) associated to asecondary reference solar module 200), then the piloting unit 7implements the piloting of the angular orientation of the solar modules3 by applying, as common orientation setpoint COC, said secondaryreference orientation setpoint COR(j), only if this secondary referencesolar module 20(j) has the highest solar energy production value P(j)during a predefined waiting time DAT.

This waiting time DAT is established depending on at least one of thefollowing parameters:

-   -   an energy consumption necessary to modify the orientation of the        solar modules 3, except for the reference solar modules 20(i),        the offset angle OFF(j) associated to the secondary reference        solar module 20 (j) having the highest solar energy production        value P(j);    -   a wear rate of mechanical members of the solar trackers 4 of the        solar modules 3, except for the reference solar modules 20 (i),        solicited during a change of orientation of the offset angle        OFF(j) associated to the secondary reference solar module 20(j)        having the highest solar energy production value P(j).

Thus, particularly in the case of diffuse radiation and/or albedo if thephotovoltaic panels are of the double-sided type, the reference solarpower plant 2 allows detecting that an offset angle OFF(j) applied withrespect to the initial orientation setpoint COI, will provide anincrease in the solar energy production, and the piloting unit 7 willpostpone this offset angle OFF(j) to the set of solar modules 3 in orderto increase the power production of the solar array 1.

Of course the implementation example mentioned above is not limiting andother improvements and details can be added to the solar array accordingto the invention, without departing from the scope of the inventionwherein other forms of solar modules and/or solar collectors may be forexample carried out.

1-11. (canceled)
 12. A method for managing a solar array comprisingsolar modules supported by single-axis solar trackers and arranged inparallel rows, the method comprising: calculating an initial orientationsetpoint; controlling an angular orientation of a first reference solarmodule according to a first reference orientation setpoint correspondingto the initial orientation setpoint; controlling an angular orientationof a second reference solar module according to a second referenceorientation setpoint corresponding to the initial orientation setpointshifted by a non-zero offset angle associated with the second referencesolar module; receiving a solar energy production value from each of thefirst and second reference solar modules; and controlling angularorientations of the solar modules other than the first and secondreference solar modules according to a reference orientation setpointassociated with a reference solar module of the first and secondreference solar modules having the highest solar energy productionvalue.
 13. The method according to claim 19, wherein, if the secondreference solar module has the highest solar energy production value fora predefined waiting time, angular orientations of the solar modulesother than the first and second reference solar modules are controlledaccording to the second reference orientation setpoint.
 14. The methodaccording to claim 20, wherein the predefined waiting time is based onan energy consumption needed to modify the angular orientations of thesolar modules other than the first and second reference solar modules.15. The method according to claim 20, wherein the predefined waitingtime is based on a wear rate of mechanical members of the single-axissolar trackers of the solar modules other than the first and secondreference solar modules.
 16. The method according to claim 19, furthercomprising: calculating an astronomical position of the Sun; andcalculating the initial orientation setpoint based on the astronomicalposition of the Sun.